Disorientation is a major chronic health problem today. Spatial memory disturbances and disorientation are common problems associated with brain damage (e.g., Alzheimer's disease, AIDS, stroke, and head injury). There is little effective nursing or medical therapy available for disoriented individuals who do not know where they are and cannot find their way from place to place. The hippocampus (HPC), a large memory structure of the brain, is thought to be essential for acquiring and retaining spatial information. With HPC damage, humans and animals become disoriented and lose their ability to use external world elements to know the environment and to find their way about. Data suggest that unilateral as well as bilateral hippocampal damage impairs acquisition of spatial information, and gender differences exist. This series of experiments will use an established animal model of human disorientation to examine the ability of male and female rats with left, right, or bilateral HPC lesions and controls to acquire and use spatial information in a new environment. A test of place navigation will be followed by tests of cue-guided navigation ability in an attempt to further describe disoriented behaviors and to identify strategies to eliminate or reduce them. In the first series of experiments, the place navigation task will test an animal's ability to locate a platform hidden under water. In the absence of any cue to mark the exact location of the platform, the animal must find it by using a fixed array of extra-pool elements. Following six days of training with four trials a day, a single visual cue will be added to mark the exact location of the platform. Animals will then receive six more days of testing, at which time a second cue will bc added to determine the effects of an environmental distractor. Time taken to locate the platform, errors in directional heading, patterns of swim paths, and exploratory activity will bc recorded at each trial. The second series of experiments will use the same place and cue-guided navigation paradigms, but the effectiveness of the cue will be enhanced by adding sound or light to it. The third series of experiments will determine whether a introduction of an enhanced single cue (I day vs 3 days) following exposure to a new environment will improve the animals' ability to find their way. This research will expand the original model of human disorientation to examine potential therapies for disoriented behaviors.